Recent advances in the study of human information processing permit direct quantitative measurement of certain self-controlled cognitive operations, called control processes. We will use these measures to study the development in children of the executive functions by which these control processes are selected, coordinated, monitored, revised, reinstated and generalized. This study is possible because executive functions can be operationally defined as reasonable spontaneous changes in control processing that result from objective changes in the demands of information processing tasks. Our aim is to chart executive function development from age six years to adulthood. Methods employed in this study will include active training in the use of effective control processes, especially for the younger children. We will study the development of executive functioning by making unannounced changes in information processing tasks and assessing children's spontaneous modifications of both trained and self-selected control processes.